1. Technical Field
The present invention relates to an engine starting device capable of starting an engine of a vehicle at high reliability even in time of lowering of a battery output voltage.
2. Related Art
Conventionally, there are known a technique of arranging a step-up circuit for stepping up battery output of a vehicle to prevent drawbacks such as a main control unit (ECU; Electrical Control Unit) in the vehicle from being reset due to lowering of a battery voltage when starting an engine as described in Japanese Unexamined Patent Publication No. 2005-218159, and a technique of arranging a step-up circuit so that an engine can be started even in a kick method in a full track two-wheeled vehicle engine starting device as described in Japanese Unexamined Patent Publication No. 2004-36494.
In order to enhance the reliability of engine start in a vehicle equipped with an engine (internal combustion engine) as a drive source such as four-wheeled vehicle or two-wheeled vehicle, a control processing unit such as a microcomputer configuring a control unit for controlling the engine start needs to be prevented from breaking down by the lowering of the battery voltage, and a starter relay needs to be reliably activated by the control of the control unit even in time of lowering of the battery voltage. The starter relay is a relay for carrying current to a starter motor to forcibly activate (so-called cranking) the engine until the engine is in a completely exploded state (state in which the internal combustion engine can maintain the rotation with own force), and is generally referred to as a magnet switch. Unless the starter relay is activated, the starter motor obviously does not activate, and the engine does not start. Thus, a configuration of arranging the step-up circuit for stepping up the battery output, and driving the controller and the starter relay with the output of the step-up circuit as in the Japanese Unexamined Patent Publication No. 2005-218159 and Japanese Unexamined Patent Publication No. 2004-36494 is considered.